Motorized sofa: 2x MY1020 BLDC, 1000w @ 36v

[bnolan]

Ok, new problem. I've got 25H chain, and it fits the 91T rear sprocket perfectly, but the 9T sprocket I have for the motor skips.

This video shows it:

https://imgur.com/a/rkE36Cz

What causes this? Is it a bad sprocket? Or is my tension / alignment bad?

You can see the problem clearly here:

 

[itsid]

Well, because the motor sprocket isn't a #25 chain but 8mm instead
(#25 is 6.35mm pitch)

you will have to order a new motor sprocket ..
the unfortunate information here is,
you will not find a #25 sprocket with nine teeth for that motor..
AFAIR 11 teeth is the minimum to wrap around the shaft

so that'll throw off your calculated gear ratio again.
dropping from 10.1:1 to 8.27:1

'sid

PS hang on 8mm should bind on the second roller, not the third...
third means slightly smaller pitch... 219 sprocket perhaps?? (7.77mm pitch)
maybe an oddling 215 (7mm pitch)
Anyways.. wrong sprocket

 

[bnolan]

It's meant to be a 25H sprocket (I ordered it from aliexpress as 25h 9t but lol). I've sourced some 11:54T sprocket and t8f chain locally so I can at least get everything hanging together while I wait for a replacement 11T 25H sprocket (from a different supplier) to come in from CHIIIIINA.

 

[itsid]

easy to test..
if the circumference of the sprocket is less than 2.6" or bigger than 2.65" it's not a #25 sprocket.

well in fact the easiest test is to wrap known #25 chain around it and see if it fits,
it doesn't, sooooo yeah

'sid

 

[bnolan]

Ok - I found something interesting. If you put the sprockets very close together so that only 3 or 4 teeth are contacting at once - then it runs quite well without skipping. I'm going to try shorten the chain and see if it works.

 

[itsid]

DON'T!

that is a terrible idea.. it's still the wrong sprocket,
and it'll eat the chain in no time (ruining not only the chain but the big sprocket as well )

plus, having only two teeth engaged puts a lot of additional stress on the sprocket teeth
speeding up such premature wear even further
[a teeth can only count as engaged if the roller is in full contact with the base]

short: it's not interesting, it's stupid I'm afraid

'sid

 

[bnolan]

Ok! Hah. I fixed it

I pulled the sprocket off and it fit the chain perfectly. So I noticed a large spring washer on the motor spindle. It was larger than the valleys in the sprocket so wasn't letting the chain sit properly. I removed the spring washer and now the chain sits on the sprocket perfectly! Phew!

But, had already ordered $60 worth of T8F chain and sprockets. :'(

Anyway - the ESCs arrived (they're bigger than the motors!), hoping to drill and mount the big sprockets tomorrow, then mount the motors and hopefully get it running!

I'm tempted to test fit the motor and just drill holes into the plywood to mount the motor with the right amount of tension on the chain for testing. Will use some remaining aluminum profile and cut some slots for a proper adjustable motor mount later on.

Here's what it looks like atm:

 

[bnolan]

Ok, got the ESC spinning the motor. Tomorrows job is to get an arduino to generate voltage ramps of 0-4v and try feeding that to the throttle wire.

edit: Tested the throttle signal line at 1.5v (nice slow speed) and 3v (scary fast with nothing connected). Hahaha. Better make sure I get my arduino code right

 

[bnolan]

Ran into problems with the chain coming off, and don't have the tools to mill a proper motor mount with slots to adjust tension. Biggest problem is ran out of time for this festival season, will have to revisit this later in the year and hopefully finish the project for summer next year!

 

[landuse]

Ran into problems with the chain coming off, and don't have the tools to mill a proper motor mount with slots to adjust tension. Biggest problem is ran out of time for this festival season, will have to revisit this later in the year and hopefully finish the project for summer next year!

To get slots, just drill a few holes and then use a file to break through them to create a slot. It looks slightly messy, but it gets the job done just fine

 

[Functional Artist]

Ran into problems with the chain coming off, and don't have the tools to mill a proper motor mount with slots to adjust tension. Biggest problem is ran out of time for this festival season, will have to revisit this later in the year and hopefully finish the project for summer next year!

Maybe try a spring loaded chain tensioner
https://www.ebay.com/itm/Motorcycle...=383323627748251d3b7ee7784bde8e0bb467378e196a

...or a slide style tensioner
https://www.ebay.com/itm/10mm-Chain...=143491129893061acce682774bd7bcdcd01f40fa75b5